Acoustics

17 pages, 2363 KB

Open AccessArticle

Analysis of Binary Encoded Signals for Underwater Acoustic Communication Under Varying Conditions

by Divaashan Pillay, Johan Venter and Daniel van Niekerk

Acoustics 2026, 8(2), 42; https://doi.org/10.3390/acoustics8020042 - 22 Jun 2026

Viewed by 285

Underwater communication is essential for marine research, yet saline environments pose significant challenges as electromagnetic waves suffer from severe attenuation and optical systems face scattering. Consequently, acoustic transmission remains the most practical method for medium- to long-range communication. This study investigates the impact [...] Read more.

Underwater communication is essential for marine research, yet saline environments pose significant challenges as electromagnetic waves suffer from severe attenuation and optical systems face scattering. Consequently, acoustic transmission remains the most practical method for medium- to long-range communication. This study investigates the impact of salinity, transmission frequency, and propagation distance on signal integrity, specifically focusing on the feasibility of using a square-wave carrier with On-Off Keying (OOK) modulation as a simpler, low-cost alternative to traditional sinusoidal frequency-shift keying (FSK). Experiments were conducted in a custom glass tank and analyzed via MATLAB. The results reveal that increased salinity and higher frequencies led to greater signal distortion and attenuation, which complicates reliable binary recovery. However, despite these environmental hurdles, the study demonstrates that square-wave OOK allows for successful binary data recovery over short distances. The findings suggest that simplified modulation schemes could potentially be used for short-range underwater communication in controlled environments, particularly where minimizing system complexity is of concern. Ultimately, the work provides valuable insights into how environmental factors influence acoustic signal integrity, offering a preliminary basis for future development of accessible and efficient underwater communication platforms targeted to shallow water communication. Full article

► Show Figures

Graphical abstract

23 pages, 3410 KB

Open AccessArticle

Human Detection of Voice-Cloned Speech Under GSM, VoLTE and VoIP Conditions

by Jakub Warzych, Michał Łuczyński and Janusz Klink

Acoustics 2026, 8(2), 41; https://doi.org/10.3390/acoustics8020041 - 17 Jun 2026

Viewed by 392

Abstract

The rapid progress of generative speech synthesis and voice-cloning technologies has enabled the creation of highly natural synthetic voices that pose a serious threat to telecommunication security. While most prior studies evaluate human ability to detect audio deepfakes using high-quality, studio-grade recordings, little [...] Read more.

The rapid progress of generative speech synthesis and voice-cloning technologies has enabled the creation of highly natural synthetic voices that pose a serious threat to telecommunication security. While most prior studies evaluate human ability to detect audio deepfakes using high-quality, studio-grade recordings, little is known about how real-world telecommunication channels affect perceptual detection. This study investigates the influence of three transmission scenarios—GSM (AMR-NB), VoLTE (AMR-WB), and VoIP with packet-loss modeling—on the human ability to distinguish natural speech from AI-generated speech. A custom speech corpus was developed, consisting of natural recordings from nine speakers and corresponding synthetic utterances generated using a state-of-the-art voice cloning system (ElevenLabs). All samples were processed through simulated telecommunication channels using real codec implementations. A listening test with 95 participants was conducted, involving binary classification (human vs. synthetic) and confidence ratings. Results show an overall detection accuracy of 54.8%, confirming that humans are poorly equipped to identify synthetic speech. Surprisingly, the highest accuracy was achieved for the narrowband GSM channel (63.7%), while VoLTE yielded the lowest performance (44.0%). The findings suggest that restricted bandwidth may emphasize prosodic irregularities typical of generative models, whereas high-quality channels mask synthetic artifacts, increasing susceptibility to voice spoofing. The results highlight the necessity of deploying additional security mechanisms in telecommunication systems relying on voice identity verification. Full article

► Show Figures

Figure 1

15 pages, 3645 KB

Open AccessArticle

Experimental Investigation of the Mach Number Influence on the Transmission Loss of Double-Tuned Straight-Through Mufflers

by Kevin Johannes Moezer, Alexander Buchele and Michael Simon Josef Walter

Acoustics 2026, 8(2), 40; https://doi.org/10.3390/acoustics8020040 - 12 Jun 2026

Viewed by 272

Abstract

Reflection silencers are installed in the exhaust system of stationary combustion engines to attenuate low-frequency noise by means of destructive interference. The acoustic properties of mufflers are experimentally determined by the standard two-load method, which only considers measurements without mean flow. In real [...] Read more.

Reflection silencers are installed in the exhaust system of stationary combustion engines to attenuate low-frequency noise by means of destructive interference. The acoustic properties of mufflers are experimentally determined by the standard two-load method, which only considers measurements without mean flow. In real engine operation, however, exhaust mass flow is always present. Measurements are significantly more complex and expensive if fluid flow is taken into account, which is why the available data is limited. Thus, the impact of mean flow on the attenuation of silencers is not clearly known yet. This work contributes to the state of the art by quantifying the influence of the Mach number on the transmission loss of double-tuned straight-through mufflers based on reproducible, noise corrected measurement results that include uncertainties. A frequency range between 20 Hz and 891 Hz is investigated at eleven different Mach numbers between 0 and 0.1 under ambient conditions. It is found that resonance peaks diminish with increasing Mach number, while other frequencies remain unaffected by mean flow. These findings can be transferred to operating conditions of stationary combustion engines and other exhaust systems. The experimental data will serve as a basis for the validation of analytical and numerical models in subsequent work. Full article

► Show Figures

Figure 1

28 pages, 756 KB

Open AccessSystematic Review

Experimental Observations of Long-Range Atmospheric Acoustics with Concurrent Meteorological Profiling: A Systematic Review

by Matthew Stengrim, Sophie Arruza, John Judge, Diego Turo and Teresa Ryan

Acoustics 2026, 8(2), 39; https://doi.org/10.3390/acoustics8020039 - 11 Jun 2026

Viewed by 395

Abstract

This systematic review summarizes experimental studies in atmospheric acoustics that quantify environmental influences on long-range sound propagation. A keyword-based search was conducted in Scopus and Google Scholar to identify relevant records. Studies were included if they were published in English between January 1977 [...] Read more.

This systematic review summarizes experimental studies in atmospheric acoustics that quantify environmental influences on long-range sound propagation. A keyword-based search was conducted in Scopus and Google Scholar to identify relevant records. Studies were included if they were published in English between January 1977 and April 2026, investigated long-range sound propagation within the human audibility range using specific sound sources, and incorporated concurrent meteorological measurements. Two reviewers worked independently to assess eligibility of the studies included in this review. Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, this systematic review surveys the methodological content of these studies with respect to sound sources, signal content and processing, microphone configuration, treatment of the ground and topography, and meteorological measurements to identify common practices. Some studies provide only limited information about the acoustic source properties, postprocessing of acoustic data, and/or configuration of meteorological measurements. Key experimental details for the 40 included studies are tabulated and summarized via histograms for reference. Most experimental acoustic studies have measured propagation within a range of 2 km on relatively flat land and have utilized tower-based meteorological measurements. The results of the studies surveyed here have implications for understanding long-range outdoor sound propagation, including development of accurate numerical models. Some contributing authors were funded by the Office of Naval Research: ONR Award N00014 24-1-2400, ONR Award N00014-24-1-2437. Full article

► Show Figures

Graphical abstract

18 pages, 5195 KB

Open AccessArticle

The Simulation Method for Ultrasonic Non-Destructive Testing of Delamination Defects in CMC Based on Air-Coupled Lamb Waves

by Da Kang, Lu Lu, Zhenggan Zhou, Yunmiao Zhang, Hong Zhang and Wenbin Zhou

Acoustics 2026, 8(2), 38; https://doi.org/10.3390/acoustics8020038 - 5 Jun 2026

Viewed by 376

Abstract

Ceramic Matrix Composite (CMC) are widely used in aerospace due to the advantages such as high-temperature resistance and lightweight properties. Detecting defects within these materials is crucial for ensuring the safety of corresponding structures. In this paper, a finite element model of CMC [...] Read more.

Ceramic Matrix Composite (CMC) are widely used in aerospace due to the advantages such as high-temperature resistance and lightweight properties. Detecting defects within these materials is crucial for ensuring the safety of corresponding structures. In this paper, a finite element model of CMC model for layered structures is established for the ultrasonic non-destructive testing. Based on the computed tomography (CT) scan images and porosity of the material, a randomly distributed pore model is constructed to investigate the effect of pores on the ultrasonic signals. Random pores are also introduced in the simulation to ensure that the model corresponds as closely as possible to reality. Moreover, the feasibility of utilizing air-coupled ultrasonic excitation to generate specific frequency Lamb waves is verified. The effect of pore presence on the signal propagation is analyzed, and the effects of layered structures at different positions and lengths on the signal propagation are investigated. The results demonstrate that the Lamb waves with a specified frequency can be excited using the method described in this paper, and the presence of pores and delamination defects can affect the propagation of the Lamb wave in CMC, in which the signal attenuation can reach up to 7.6 dB. Full article

► Show Figures

Figure 1

20 pages, 5559 KB

Open AccessArticle

Identification of Dominant Factors and Generation Mechanisms for Guided-Wave Reflections in Prestressed Strand Anchorage Segments

by Zheng Zheng, Jiang Xu, Can Wang, Guoming Li and Chengcai Liu

Acoustics 2026, 8(2), 37; https://doi.org/10.3390/acoustics8020037 - 5 Jun 2026

Viewed by 349

Abstract

Prestressed steel strands transfer structural loads through complex anchorage systems. During through-anchorage ultrasonic guided-wave inspection, strong reflections generated in the anchorage segment may obscure defect-related echoes and create blind zones in the received signals. This study investigates the generation mechanisms of these anchorage-induced [...] Read more.

Prestressed steel strands transfer structural loads through complex anchorage systems. During through-anchorage ultrasonic guided-wave inspection, strong reflections generated in the anchorage segment may obscure defect-related echoes and create blind zones in the received signals. This study investigates the generation mechanisms of these anchorage-induced reflections and evaluates the relative roles of stress-induced acoustoelastic impedance variation and load-dependent interfacial contact evolution. An acoustoelastic finite element model is first used to estimate the reflection contribution caused by stress concentration alone. The results show that the stress-induced reflection remains weak, with the reflection coefficient remaining below 0.0125 even at 80% of the ultimate tensile strength. A sensitivity-based equivalent spring-contact model is then employed to examine whether effective strand–wedge and wedge–anchorage interfacial stiffness variations can generate anchorage reflections with comparable order of magnitude and load-dependent trends. The contact-based model produces much stronger reflections, and roughness-sensitivity analysis indicates that the load-dependent trend is not governed by a single nominal roughness assumption. Multi-specimen stepwise tensioning experiments show repeatable load-dependent reflection trends at both 80 kHz and 240 kHz. The results therefore suggest that, within the investigated geometry and loading range, interfacial contact evolution is a more plausible dominant contributor to anchorage-induced guided-wave reflections than stress-induced acoustoelastic impedance variation. This work focuses on the physical origin of anchorage reflections and provides a mechanistic basis for interpreting anchorage-induced interference in future through-anchorage defect detection. Full article

► Show Figures

Figure 1

14 pages, 1680 KB

Open AccessArticle

Distribution-Aware, Risk-Sensitive (DA-RS-FxNLMS) Active Noise Control for Non-Gaussian Acoustic Environments

by Pushpraj Tanwar, Ajay Somkuwar and Rakesh Kumar Gumasta

Acoustics 2026, 8(2), 36; https://doi.org/10.3390/acoustics8020036 - 4 Jun 2026

Viewed by 339

Abstract

Active noise control (ANC) in real-world acoustic environments frequently faces impulsive and heavy-tailed noise disturbances, which degrade the performance significantly and lead to slow convergence. This work proposes a dynamically adaptive distribution-aware risk-sensitive filtered-x normalized least mean square (DA-RS-FxNLMS) method for efficient ANC [...] Read more.

Active noise control (ANC) in real-world acoustic environments frequently faces impulsive and heavy-tailed noise disturbances, which degrade the performance significantly and lead to slow convergence. This work proposes a dynamically adaptive distribution-aware risk-sensitive filtered-x normalized least mean square (DA-RS-FxNLMS) method for efficient ANC under a non-Gaussian and impulsive scenario. The proposed ANC framework employs a correntropy-based risk-sensitive exponential cost function, which incorporates higher-order statistics and adapts to the error distribution. Further, an adaptive and dynamically adjusted kernel width mechanism tracks the time-varying noise characteristics. The normalized filtered-x structure provides stability under secondary path uncertainty. Simulation is carried out by applying α-stable noise to create an impulsive noise environment, which is produced by the Chambers-Mallows-Stuck method. The outcomes of the proposed method are compared with the baseline methods, showing that the proposed method achieves a noise reduction of 7.02 dB, a significant 40% faster convergence, and improved robustness under strong impulsive noise conditions with α = 1.2. The outcome confirms that the proposed method efficiently delivers a promising solution for the ANC system. To the best of our knowledge, for the first time, a unified ANC framework integrates distribution-aware, risk-sensitive learning, adaptive correntropy kernel estimation, and filtered-x normalization for non-Gaussian acoustic environments. Full article

► Show Figures

Figure 1

20 pages, 1845 KB

Open AccessReview

A Review of Microperforated Panel-Based Structures for Low Frequency Sound Absorption

by Santiago Ortiz, María Cuesta and Pedro Cobo

Acoustics 2026, 8(2), 35; https://doi.org/10.3390/acoustics8020035 - 30 May 2026

Cited by 1 | Viewed by 719

Abstract

The use of sound absorption materials has traditionally been restricted to medium-to-high frequencies due to their limitations at low frequencies, where the large wavelength of sound waves imposes rather bulky solutions. However, recent materials and designs allow for the absorption of sound waves [...] Read more.

The use of sound absorption materials has traditionally been restricted to medium-to-high frequencies due to their limitations at low frequencies, where the large wavelength of sound waves imposes rather bulky solutions. However, recent materials and designs allow for the absorption of sound waves with more practical sizes and weights, reviving interest in this frequency range. Some of these low-frequency absorbers, also named acoustic metamaterials or sub-wavelength sound absorbers, based on microperforated panels, are reviewed in this article. These include multilayer and multicavity microperforated panels, hybrid passive–active absorbers, multiple Helmholtz resonators, and microperforated panels with labyrinthine cavities or sonic black holes. Full article

► Show Figures

Figure 1

34 pages, 5551 KB

Open AccessReview

Vibration and Sound Radiation of Percussion Instruments: A Finite Element-Based Review

by Evaggelos Kaselouris and Vasilis Dimitriou

Acoustics 2026, 8(2), 34; https://doi.org/10.3390/acoustics8020034 - 28 May 2026

Viewed by 750

Abstract

Percussion instruments exhibit complex vibrational behavior characterized by transient excitation, high modal density, and strong structural–acoustic coupling. Numerical modeling—especially the finite element method (FEM)—has become essential for analyzing realistic geometries, material heterogeneity, and fluid–structure interaction. This review systematically synthesizes FEM-based studies on percussion [...] Read more.

Percussion instruments exhibit complex vibrational behavior characterized by transient excitation, high modal density, and strong structural–acoustic coupling. Numerical modeling—especially the finite element method (FEM)—has become essential for analyzing realistic geometries, material heterogeneity, and fluid–structure interaction. This review systematically synthesizes FEM-based studies on percussion instruments, organized by their physical classification into idiophones and membranophones. The present work thematically compares modeling strategies and their trade-offs and highlights actionable research gaps. FEM and coupled FEM–boundary element (BEM) approaches applied to bars, plates, shells, membranes, and vibroacoustic systems are reviewed, with emphasis on modal behavior, tuning strategies, excitation mechanisms, nonlinear phenomena, and fluid–structure interaction. A key feature is the consistent validation of simulations against experimental measurements. The analysis reveals that while FEM is mature for modeling bars, plates, shells, and single-membrane systems, significant gaps remain: bar–resonator coupling and damping/residual stress modeling in idiophones, coupled clapper–bell–air simulations for bells, and fully coupled double-membrane simulations for drums. The latter directly affects predictions of modal frequencies, decay rates, and timbre. The review concludes by identifying priority research directions: fully coupled double-membrane models, material nonlinear viscoelasticity, efficient FEM–BEM coupling, and integration of performer-informed excitation for sound synthesis. Full article

► Show Figures

Figure 1

18 pages, 5182 KB

Open AccessArticle

Efficient Dust Removal and Energy Recovery of PV Modules via Low-Frequency Ultrasonic Vibration: Experiment and Dynamic Analysis

by Yutao Wang, Tieyu Gao, Mengling Jiang, Jianying Gong, Xiaojun Xie and Zichen Song

Acoustics 2026, 8(2), 33; https://doi.org/10.3390/acoustics8020033 - 25 May 2026

Viewed by 519

Abstract

Dust accumulation on photovoltaic (PV) modules reduces power generation efficiency, and traditional water-based cleaning is impractical in arid regions. Inspired by the classical acoustic phenomenon of Chladni figures—specifically the mechanism where an acoustic standing wave field drives the regular migration and accumulation of [...] Read more.

Dust accumulation on photovoltaic (PV) modules reduces power generation efficiency, and traditional water-based cleaning is impractical in arid regions. Inspired by the classical acoustic phenomenon of Chladni figures—specifically the mechanism where an acoustic standing wave field drives the regular migration and accumulation of particles—this study proposes a waterless dust removal method using low-frequency ultrasonic vibration via piezoelectric excitation. Impedance analysis identifies optimal electromechanical coupling at 28 kHz. Experiments demonstrate that higher driving voltages accelerate cleaning, with recovery rates saturating beyond 125 V. Notably, intense friction and collisions between particles within high-density dust layers consume substantial kinetic energy, significantly multiplying the required cleaning time. Macroscopic transport analysis reveals that dust removal relies on the synergy of vibration-induced adhesion decoupling and gravity-driven transport. Sufficient tangential gravity is crucial for macroscopic particle removal, and tilt angles above 30° provide the necessary downward driving force to ensure smooth particle sliding. Under optimal conditions, the system achieves an over 97% short-circuit current recovery at a low power consumption of ~10 W, providing a theoretical basis for waterless PV self-cleaning systems. Full article

► Show Figures

Figure 1

17 pages, 1953 KB

Open AccessArticle

Theoretical Modeling and Experimental Verification of the First and Second Underwater Bubble Pulsation Period

by Fan Yang, Hao Yin, Yu Lu, Xuexu Li and Xinliang Pang

Acoustics 2026, 8(2), 32; https://doi.org/10.3390/acoustics8020032 - 20 May 2026

Viewed by 468

Abstract

The study of bubble pulsation from underwater explosions is critical for applications in marine resource exploration, underwater demolition, and offshore engineering. However, the existing research methods have significant limitations: Laboratory experiments struggle to replicate the dynamic decompression during the process of bubble rising. [...] Read more.

The study of bubble pulsation from underwater explosions is critical for applications in marine resource exploration, underwater demolition, and offshore engineering. However, the existing research methods have significant limitations: Laboratory experiments struggle to replicate the dynamic decompression during the process of bubble rising. Field experiments in seas or lakes find it difficult to systematically cover complex parameter ranges. Furthermore, theoretical calculations face the problems of accurately coupling the bubble pulsation with its buoyancy-driven ascent. Therefore, this paper proposes a novel method for calculating the bubble pulsation period of underwater explosions. This method accurately simulates the pulsation and buoyancy-driven ascent of an underwater explosion bubble. Based on the bubble’s energy attenuation characteristics, it establishes the relationship between the pulsation period, TNT equivalent, and ambient hydrostatic pressure. To verify the accuracy of the method, we conducted underwater explosion experiments in the South China Sea with varying TNT equivalents and detonation depths. Abundant bubble pulsation period data of underwater explosions were obtained spatially by deploying hydrophone arrays at various depths. The close agreement between the theoretical predictions and the experimental results confirms the accuracy of the proposed method. By matching the measured values of the first pulsation period and the ratio of the second pulsation period to the first against a database of theoretical curves, a combination of depth and charge equivalent that satisfies both values can be identified, thereby enabling the inversion of the explosion parameters. Full article

► Show Figures

Figure 1

14 pages, 2202 KB

Open AccessArticle

Surrogate-Based Uncertainty Quantification for Coupled Structural–Acoustic Problems

by Younes Koulou, Hakima Reddad, Norelislam El Hami, Nabil Hmina and Abdelkhalak El Hami

Acoustics 2026, 8(2), 31; https://doi.org/10.3390/acoustics8020031 - 14 May 2026

Viewed by 540

Abstract

This paper presents a surrogate-based uncertainty quantification (UQ) framework for coupled structural–acoustic systems subject to material and geometric variability. The proposed methodology integrates the Finite Element Method (FEM) with two metamodeling techniques—the Quadratic Response Surface (QRS) and Kriging—and Monte Carlo Simulations (MCS), to [...] Read more.

This paper presents a surrogate-based uncertainty quantification (UQ) framework for coupled structural–acoustic systems subject to material and geometric variability. The proposed methodology integrates the Finite Element Method (FEM) with two metamodeling techniques—the Quadratic Response Surface (QRS) and Kriging—and Monte Carlo Simulations (MCS), to efficiently characterize the probabilistic behavior of the acoustic response. Two accuracy metrics (cross-validation error and prediction error) are used to validate the surrogate models. Numerical experiments demonstrate that the Kriging metamodel trained with 30 Latin Hypercube Sampling (LHS) points achieves superior predictive accuracy, with a Relative Maximum Error of 4.125 × 10⁻⁷. Monte Carlo Simulations conducted via the Kriging surrogate reduce the computational cost by more than six orders of magnitude compared to direct FEM-based MCS, while maintaining high accuracy. The proposed framework is validated on a rectangular cavity coupled with two flexible aluminum plates, and provides an efficient and accurate tool for vibro-acoustic UQ in complex engineering systems. Full article

► Show Figures

Figure 1

17 pages, 2999 KB

Open AccessArticle

An Approximate Analytical Method for Predicting Attenuation Due to Ground Effect

by Keith Attenborough

Acoustics 2026, 8(2), 30; https://doi.org/10.3390/acoustics8020030 - 11 May 2026

Viewed by 515

Abstract

An approximate analytical model for the variation of A-weighted broadband sound levels with distance over flat acoustically soft ground from a source of known sound power depends on the reduction in low frequency content in noise spectra due to A-weighting. Also, it assumes [...] Read more.

An approximate analytical model for the variation of A-weighted broadband sound levels with distance over flat acoustically soft ground from a source of known sound power depends on the reduction in low frequency content in noise spectra due to A-weighting. Also, it assumes a weak linear sound speed gradient and a frequency independent attenuation coefficient for air absorption. The model introduces adjustable frequency independent parameters for ground effect, turbulence and atmospheric refraction. An additional parameter allows for the source being located over acoustically hard ground. Predictions of the model are compared with measurements over several ground surfaces. The approximate model predicts a more rapid reduction in sound attenuation due to ground effect with increasing mean propagation path height than the simplified method in a widely used international standard. Moreover, predictions of A-weighted sound levels from onshore wind turbines using the approximate analytical method compare with data and numerical simulations better than the simplified and octave band methods in the international standard and the Swedish standard method. Full article

► Show Figures

Figure 1

13 pages, 13564 KB

Open AccessArticle

Evaluation of the Effect of Vibration and Acoustic Signals in a Class II Biological Safety Cabinet on Wound Healing in Keratinocytes

by Mete Öğüç and Zeynep Güneş Özünal

Acoustics 2026, 8(2), 29; https://doi.org/10.3390/acoustics8020029 - 29 Apr 2026

Viewed by 763

Abstract

Class II biological safety cabinets (BSCs) are designed to protect the user, the product, and the laboratory environment by maintaining HEPA-filtered airflow; however, their fans, alarms, and structural resonances introduce acoustic and vibrational stimuli that may confound mechanosensitive cell-culture assays. In this study, [...] Read more.

Class II biological safety cabinets (BSCs) are designed to protect the user, the product, and the laboratory environment by maintaining HEPA-filtered airflow; however, their fans, alarms, and structural resonances introduce acoustic and vibrational stimuli that may confound mechanosensitive cell-culture assays. In this study, we characterized the vibroacoustic environment of a cell-culture laboratory and a Class II BSC, selected representative tray locations based on measured and modeled stimuli, and evaluated in vitro wound closure in HaCaT keratinocytes using a scratch assay under alarm-induced acoustic exposure. Wound closure after 24 h was quantified using a relative area-closure metric defined as one minus the ratio of wound area at 24 h to wound area at 0 h. For each biological replicate (one flask and one scratch), two non-overlapping image regions were treated as technical subsamples and averaged to obtain a single flask-level value. Three independent experimental runs were performed, each including one flask per tray point, yielding n equals 3 independent flasks per tray point. Mean wound closure values were 73.7 percent plus or minus 15.6 percent, 75.6 percent plus or minus 7.2 percent, and 79.4 percent plus or minus 14.8 percent for tray points P1, P5, and P6, respectively (mean plus or minus standard deviation). No statistically significant differences were detected among points (one-way ANOVA on flask-level values, F equals 0.15, p equals 0.86). These findings highlight that BSC-associated acoustic and vibration stimuli should be documented when interpreting scratch-assay outcomes and motivate larger, sham-controlled studies to resolve small effect sizes relevant for assay reproducibility. Full article

(This article belongs to the Special Issue Vibration and Noise (3rd Edition))

► Show Figures

Figure 1

19 pages, 5566 KB

Open AccessArticle

Noise Characteristics and Multi-Dimensional Sound Quality Evaluation of High-Frequency Transformers Under Non-Sinusoidal Excitation

by Cai Zeng, Li Li, Yexin Zhu, Xing Du, Jie Zhang, Xiaoqiong He and Xinbiao Xiao

Acoustics 2026, 8(2), 28; https://doi.org/10.3390/acoustics8020028 - 26 Apr 2026

Viewed by 741

Abstract

High-frequency transformer (HFT) noise is a pivotal indicator of equipment performance. To conduct a comprehensive evaluation, this study systematically performed testing and evaluation on the noise generated by a 70 kW HFT under no-load conditions. Acoustic data were collected using acoustic sensors and [...] Read more.

High-frequency transformer (HFT) noise is a pivotal indicator of equipment performance. To conduct a comprehensive evaluation, this study systematically performed testing and evaluation on the noise generated by a 70 kW HFT under no-load conditions. Acoustic data were collected using acoustic sensors and a head-and-torso simulator, followed by an analysis of noise characteristics focusing on the impacts of voltage levels and operating frequencies. A multi-dimensional evaluation of HFT noise was carried out using sound quality parameters to unravel its intrinsic attributes under electrical parameter excitation. The key findings are as follows: HFT noise exhibits steady-state time-domain behavior and distinct tonal frequency-domain features; the dominant frequency is twice the operating frequency, with prominent harmonics. The noise intensity increases with the voltage levels (~47.0 dB (A) at 200 V to ~72.0 dB (A) at 750 V at 5 kHz) but decreases with the operating frequencies (~82.0 dB (A) at 4 kHz to ~47.0 dB (A) at 10 kHz at 750 V). This study establishes correlations between the electrical parameters and sound quality metrics; the loudness, sharpness, tone-to-noise ratio and prominence ratio are sensitive to the electrical parameters of HFT. Single-frequency noise from HFT exhibits remarkable perceptual salience, exacerbating the perceived annoyance. Thus, HFT design should prioritize reducing single-frequency noise to alleviate such issues. Full article

► Show Figures

Figure 1

21 pages, 54567 KB

Open AccessArticle

Application and Development of Aircraft Flyover Measurements in China

by Haoyuan Dong, Cheng Wei Lee, Yuqi Zhou and Wei Ma

Acoustics 2026, 8(2), 27; https://doi.org/10.3390/acoustics8020027 - 23 Apr 2026

Viewed by 555

Abstract

Aircraft flyover measurements are used to record the acoustic pressure signals generated by large civil aircraft as they fly over a large-scale microphone array deployed on the ground, thereby obtaining the spatial distribution of aircraft airframe noise and providing technical support for aircraft [...] Read more.

Aircraft flyover measurements are used to record the acoustic pressure signals generated by large civil aircraft as they fly over a large-scale microphone array deployed on the ground, thereby obtaining the spatial distribution of aircraft airframe noise and providing technical support for aircraft noise reduction. Aircraft flyover measurements have been widely applied in the research and development of numerous large civil aircraft in Europe and North America since the 1990s. In recent years, aircraft flyover measurements have also been extensively adopted in China, particularly with the rapid development of COMAC C919 large civil aircraft. Computer vision techniques have also been applied to microphone position calibration and aircraft trajectory determination in measurements, which has effectively improved measurement efficiency and accuracy. This paper presents an integrated procedure for aircraft flyover measurements of large civil aircraft in China, including microphone array design, installation, and calibration, noise acquisition system setup and data acquisition, aircraft trajectory determination, and data processing. Full article

► Show Figures

Figure 1

36 pages, 6746 KB

Open AccessArticle

An Archaeoacoustic Analysis of a Single-Nave Hall in the Cellars of Diocletian’s Palace in Split, Croatia

by Mateja Nosil Mešić, Marko Horvat and Zoran Veršić

Acoustics 2026, 8(2), 26; https://doi.org/10.3390/acoustics8020026 - 20 Apr 2026

Viewed by 777

Abstract

Diocletian’s palace with its cellars represents one of the most important cultural heritage sites of the ancient Roman civilisation on the present-day Croatian territory. The cellar complex has been rediscovered only recently and has been preserved remarkably well due to its centuries-long concealment [...] Read more.

Diocletian’s palace with its cellars represents one of the most important cultural heritage sites of the ancient Roman civilisation on the present-day Croatian territory. The cellar complex has been rediscovered only recently and has been preserved remarkably well due to its centuries-long concealment beneath mediaeval urban matrices. An archaeoacoustic analysis was performed on a selected single-nave hall as a small part of this complex. A model of the hall was developed in room acoustics simulation software and calibrated based on the results of field measurements. Acoustic suitability of the hall for speech-based events and music performances was then evaluated according to contemporary objective criteria, and the findings were compared with the results of similar studies performed on other heritage sites. The hall was found to be very well suited for speech in terms of intelligibility and mid-frequency reverberation, thus showing potential for revitalisation, with excessive low-frequency reverberation in the hall and reduced audibility in the farthest part of the audience as potential issues. With a feasible audience size, the hall is not reverberant enough for music performances but provides high clarity. In terms of sound strength, the hall is suitable for solo performers or small ensembles. Excessive perceptive broadening of the sound source is expected due to strong early lateral energy. In terms of traditional Dalmatian a cappella singing, the acoustics of the hall are likely to support and enhance such performances. Full article

(This article belongs to the Collection Historical Acoustics)

► Show Figures

Figure 1

22 pages, 14002 KB

Open AccessArticle

Mesoscale Eddy Characteristics and Their Influence on Acoustic Propagation in the Kuroshio Boundary Region

by Shisong Zhang, Xiaofang Sun and PingBo Wang

Acoustics 2026, 8(2), 25; https://doi.org/10.3390/acoustics8020025 - 20 Apr 2026

Viewed by 582

Abstract

This study focuses on how mesoscale eddies at the Kuroshio boundary in the East China Sea modulate underwater acoustic propagation. Using high-resolution reanalysis data from the Hybrid Coordinate Ocean Model (HYCOM) and validated acoustic ray-tracing simulations, the OW + SLA method is employed [...] Read more.

This study focuses on how mesoscale eddies at the Kuroshio boundary in the East China Sea modulate underwater acoustic propagation. Using high-resolution reanalysis data from the Hybrid Coordinate Ocean Model (HYCOM) and validated acoustic ray-tracing simulations, the OW + SLA method is employed for eddy identification and classification. Statistical analysis of 120 eddy events from 2015 to 2020 clarifies their seasonal variation characteristics. Warm eddies shift the convergence zone 15–30 km away from the sound source and broaden it by 20–40%, while cold eddies shift it 10–25 km toward the source and narrow it by 15–35%. A linear relationship exists between eddy amplitude and acoustic transmission loss (TL = 72.4 + 0.42 h, R² = 0.61), where TL is the transmission loss in decibels (dB) and h is the eddy amplitude in meters (m), and there are depth-dependent transmission loss modulation effects. These results provide practical guidance not only for sonar system design and acoustic communication optimization but also for error correction in underwater acoustic navigation systems operating in eddy-prone environments. Full article

► Show Figures

Figure 1

11 pages, 1626 KB

Open AccessArticle

Numerical Investigation of Stiffness Saturation and Damping Effects on Underwater Acoustic Radiation of Composite Grillage Structures

by Dajiang Wu, Zhenlong Zhou and Yuelin Zhang

Acoustics 2026, 8(2), 24; https://doi.org/10.3390/acoustics8020024 - 1 Apr 2026

Viewed by 782

Abstract

Enhancing the vibroacoustic performance of underwater vehicles remains a critical challenge in marine engineering. Increasing geometric stiffness is a conventional strategy to suppress vibration, yet its effectiveness in reducing underwater sound radiation can be practically limited. This paper presents a numerical investigation of [...] Read more.

Enhancing the vibroacoustic performance of underwater vehicles remains a critical challenge in marine engineering. Increasing geometric stiffness is a conventional strategy to suppress vibration, yet its effectiveness in reducing underwater sound radiation can be practically limited. This paper presents a numerical investigation of the vibroacoustic response of composite grillage sandwich structures, with a focus on separating the contributions of geometric stiffening and core damping. A coupled acoustic structural model is developed based on the equivalent single layer theory and implemented in a finite element framework, then validated against analytical benchmark solutions. The parametric study reveals a stiffness saturation phenomenon in the acoustic domain. Although increasing rib height significantly reduces the mean square velocity, the radiated sound power reaches a saturation plateau and can even show a slight rebound at higher frequencies. This behavior is attributed to an increase in structural phase velocity that shifts modal components toward a more efficient radiation regime, thereby increasing radiation efficiency. To address this limitation, the damping modulation role of the core material is examined. The results show that introducing a high damping core into the grillage skeleton suppresses broadband noise and resonance peaks, without a comparable rise in radiation efficiency that may accompany geometric stiffening. The study indicates that a hierarchical synergistic design strategy that uses geometric stiffness for load bearing and low frequency control, while leveraging core damping to mitigate the acoustic saturation limit, provides useful physical insight into more efficient noise control approaches than purely stiffness based approaches. Full article

► Show Figures

Figure 1

20 pages, 8560 KB

Open AccessArticle

Modelling of Shell Trumpet Overtones and Acoustics of Helicoidal Geometries

by Marcel-André Ramírez-Trocherie, Pablo Padilla, Francisca Zalaquett and Martín Salinas-Vázquez

Acoustics 2026, 8(2), 23; https://doi.org/10.3390/acoustics8020023 - 1 Apr 2026

Viewed by 724

Abstract

In this work, the propagation of acoustic waves in shell trumpets is explored, and the overtones generated by them are studied. We consider different shell geometries, for which their particular morphology is taken into account. This impacts the fundamental frequencies as well as [...] Read more.

In this work, the propagation of acoustic waves in shell trumpets is explored, and the overtones generated by them are studied. We consider different shell geometries, for which their particular morphology is taken into account. This impacts the fundamental frequencies as well as the overtones. An analytical model based on differential equations is developed to predict these overtones and compared with real recordings of some shell trumpets belonging to several collections in Mexico (experimental results). As a consequence, the notes of archaeological shells that cannot be played due to their physical damage are estimated. Full article

(This article belongs to the Special Issue The Past Has Ears: Archaeoacoustics and Acoustic Heritage)

► Show Figures

Figure 1

25 pages, 16006 KB

Open AccessArticle

Underwater Target Recognition with Fusion of Multi-Domain Temporal Features

by Xiaochun Liu, Chenyu Wang, Yunchuan Yang, Xiangfeng Yang, Youfeng Hu and Jianguo Liu

Acoustics 2026, 8(2), 22; https://doi.org/10.3390/acoustics8020022 - 25 Mar 2026

Viewed by 1055

Abstract

The dynamic nature of acoustic environments—particularly the fluctuation of underwater channels and time-varying target observation angles—poses significant challenges for active sonar target recognition, a problem further aggravated by the scarcity of labeled training samples. To address these limitations, this paper proposes a novel [...] Read more.

The dynamic nature of acoustic environments—particularly the fluctuation of underwater channels and time-varying target observation angles—poses significant challenges for active sonar target recognition, a problem further aggravated by the scarcity of labeled training samples. To address these limitations, this paper proposes a novel recognition method enabling deep fusion of multi-domain temporal features extracted from target echoes. First, complementary features are extracted across spatial, time–frequency, and Doppler domains to achieve a comprehensive and discriminative representation of targets. Subsequently, we introduce a feature vector-level fusion mechanism designed specifically for few-shot learning, integrating a meta-knowledge-driven multi-stream feature extractor with an internal memory module within the feature tensor framework. This architecture constitutes the Multi-domain Temporal Feature Fusion Recognition Network (MTFF-RNet). The proposed approach is evaluated on a hybrid dataset combining simulated and experimental data, achieving a high recognition accuracy of 96.2% for both targets and interferents. Experimental results demonstrate that MTFF-RNet significantly enhances robustness and adaptability under varying underwater acoustic conditions and dynamic viewing geometries. Full article

► Show Figures

Figure 1

18 pages, 2903 KB

Open AccessArticle

Infrasound Signal Classification Fusion Model Based on Double-Branch and Multi-Scale CNN and LSTM

by Hao Yin, Yu Lu, Yunhui Wu, Wei Cheng, Xinliang Pang and Peng Li

Acoustics 2026, 8(2), 21; https://doi.org/10.3390/acoustics8020021 - 24 Mar 2026

Viewed by 769

Abstract

The accurate classification of infrasound events is significant in natural disaster warning, verification of nuclear test bans and geophysical research. Current deep learning-based classification methods mostly focus on denoised and filtered signals. To simplify the process, avoid information loss, and address the issues [...] Read more.

The accurate classification of infrasound events is significant in natural disaster warning, verification of nuclear test bans and geophysical research. Current deep learning-based classification methods mostly focus on denoised and filtered signals. To simplify the process, avoid information loss, and address the issues of incomplete feature extraction by single-scale convolution kernels and the potential loss of physical information by single models, this paper directly utilizes raw infrasound signals and proposes two fusion classification models based on multi-scale Convolutional Neural Network (CNN) and Long Short-Term Memory (LSTM). Experiments were conducted on a typical infrasound signal dataset (comprising four signal types: mountain-associated waves, auroral infrasound waves, volcanic eruptions, and microbaroms). The performances of the two models were compared in terms of accuracy, convergence speed, and stability. The results indicate that both models achieve classification accuracies exceeding 99% with optimal parameter combinations. The dual-branch multi-scale CNN-LSTM model generally outperforms the multi-scale CNN-LSTM model in classification accuracy, while also demonstrating faster convergence speed and better stability. Addressing the class imbalance in the dataset, evaluations using precision, recall, and F1-score further validated the effectiveness of the proposed models. This study demonstrates that the proposed methods can effectively achieve end-to-end classification of raw infrasound signals and are competitive with existing techniques. Full article

► Show Figures

Figure 1

Journal Menu

Journal Browser

Acoustics, Volume 8, Issue 2 (June 2026) – 22 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI